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Old 02-16-2010, 09:48 PM   #1
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Default MS missing issues.

Ever since I've had this MS in the car it's been missing usually on the freeway while cruising sometimes at full throttle too! It does it from 2,500 rpms and up randomly. It seems to be getting worse though. However 25% of the time it will not do it and it will run just fine. If I turn the car off leave it for a few minutes and start it again there's a 25% chance that it won't do it. But if it does it's going to keep doing it the entire drive untill I turn it off and try again.

The missing is more like the MS is trying to turn off the engine. It cuts fuel from what I can see on the wideband and probably spark too and the tachometer jumps down 500 rpm. It usually hits only once every minute or so but it seems to be happening more and more often. Sometimes it will hit two or three times in a row! Do you realize what that feels like when your trying to accelerate or cruise? It realy seems to like to do it at -9psi while cruising but that is not the only time it does it's just the most often time, if that even has anything to do with it.

I wish for once I could help someone on this forum with their MS but instead it seems to always be me posting my problems, ugh! At least it runs right? lol
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Old 02-17-2010, 10:26 AM   #2
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Do you have a data log of the misfires happening that you could post, along with your MSQ? One tip - if you want to mark where the misfires are happening, press the space bar when it misfires, and this will put a manual mark in the log.
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Old 02-17-2010, 11:29 AM   #3
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If there is a sharp drop in the tach that occurs with the misfire, on a 1.6 car it's often a problem with the ignitor.

Have you ever flashed firmware without disconnecting the ignitor? This is exactly the problem that happens if you do. Your datalog might reveal something different, but the problems presented sound like your ignitor is failing for one reason or another.
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Old 02-17-2010, 12:01 PM   #4
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Good advice here. And true.

The other common culprit in the '90-'97 cars is the CAS (cam angle sensor) which is installed at the back of the intake cam. This device outputs two squarewave signals which give the ECU positional information on where the cam and crank are in the cycle.

Unfortunately, these sensors seem to be a tad squirrelly. Combine that with the fact that the standard setup for putting a second trigger input on the MS 3.0 board is, well, rather basic, and you have the possibility for noise on the line to be interpreted as false triggers. I suspect that this is why Matt is asking you for a log file- when this happens, it shows up as a very obvious spike in the RPM data.
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Old 02-17-2010, 07:52 PM   #5
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Can someone explain how to data log? I'm still learning this stuff I pretty much just know how to build and tune the thing. I didn't see anywhere to open a data log window in mega tune.
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Old 02-17-2010, 07:58 PM   #6
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First, if it were me, I would ditch megatune and download tunerstudio. Secondly, I cant remember if its under file, or maybe communications? Either way, its under one of the menus at the top. [menu]->[start datalog] IIRC. I havn't used megatune in so long though...
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Old 02-22-2010, 08:06 PM   #7
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Thanks. I'll try it out. I been gone for a while. Out snowboarding, it was a blast. Now I'm back at it with this car with a fresh mind and more tolerance for it haha.
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Old 02-23-2010, 12:33 AM   #8
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Quote:
Originally Posted by Cookie Monster View Post
Ever since I've had this MS in the car it's been missing usually on the freeway while cruising sometimes at full throttle too! It does it from 2,500 rpms and up randomly. It seems to be getting worse though. However 25% of the time it will not do it and it will run just fine. If I turn the car off leave it for a few minutes and start it again there's a 25% chance that it won't do it. But if it does it's going to keep doing it the entire drive untill I turn it off and try again.

The missing is more like the MS is trying to turn off the engine. It cuts fuel from what I can see on the wideband and probably spark too and the tachometer jumps down 500 rpm. It usually hits only once every minute or so but it seems to be happening more and more often. Sometimes it will hit two or three times in a row! Do you realize what that feels like when your trying to accelerate or cruise? It realy seems to like to do it at -9psi while cruising but that is not the only time it does it's just the most often time, if that even has anything to do with it.

I wish for once I could help someone on this forum with their MS but instead it seems to always be me posting my problems, ugh! At least it runs right? lol
I had similar problem (same symptoms) with my setup. (MS2 with low-z injectors). I soldered a 330nF capacitor to the boot jumper on the main board and also added a 3300uF and 4.7uF capacitors in parallel between 12V and ground. I later drove the car for about 50 miles and haven't had any misfires.

Hope this helps.
-Raj
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Old 02-23-2010, 06:47 PM   #9
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Quote:
Originally Posted by redrider706 View Post
I had similar problem (same symptoms) with my setup. (MS2 with low-z injectors). I soldered a 330nF capacitor to the boot jumper on the main board and also added a 3300uF and 4.7uF capacitors in parallel between 12V and ground. I later drove the car for about 50 miles and haven't had any misfires.

Hope this helps.
-Raj
Can you tell me what that does for you? I have a MS version 3 main board.

My battery in my laptop is dead so I didn't get to datalog today. I'm going to plug it into the car next time.
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Old 02-23-2010, 06:52 PM   #10
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yeah go ahead and datalog. check to see if some of these are resets or just RPM spikes. I have an issue where i get a bad signal, it reads like 30,000rpms for 1 blip , which turns on the rev limiter for 1 blip...which makes the car stumble.

It happens on highway cruise. It is a PITA but i havent looked too much into it.

I have MS1 Hi-res on a 96 in parallel with 550cc rx7 inj
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Old 02-23-2010, 07:56 PM   #11
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Quote:
Originally Posted by Cookie Monster View Post
Can you tell me what that does for you? I have a MS version 3 main board.

My battery in my laptop is dead so I didn't get to datalog today. I'm going to plug it into the car next time.
I was basically following Jerry (DIY Autotune) post on one of the threads here. He was saying that the 12V line had some noise and so they added the capacitors to the 12V line in the DIYPNP kits. The capacitor on the boot jumper comes from the discussion on the MSExtra forum about injector noise / voltage spikes from using low-z injectors on MS2.

But, before all this get a datalog and see what's going on. I saw clear sync loss when I was having the stumbles and the reason for sync loss was 39.

-Raj

Last edited by redrider706; 02-23-2010 at 08:04 PM. Reason: Typo
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Old 02-24-2010, 09:21 PM   #12
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Same thing happens to me, misses at highway cruise 3-4k rpm range. Pretty random. After reading this thread I pulled a datalog and sure enough, there were rpm spikes to 10k rpm. About the same time injector pulse drops to zero and sometimes spark, which confirms the rev limiter.

Wondering if running a new separate shielded wire for the CAS would help. Now I think of it, I don't remember ever having this problem before toyota cops.
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Old 02-24-2010, 10:23 PM   #13
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I couldn't data log today. I tried to open it up under FILE/DATALOG/RECORD and only got a window wanting me to save it in a car1 folder. blah.
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Old 03-02-2010, 11:10 PM   #14
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How do I start a Datalog? I tried to pull up Megalog Viewer but it says 'Java runtime enviroment not found!' Then gives me a website link that no longer exists.

If I get this problem fixed it will be running perfectly on MegaSquirt!!! :^D
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Old 03-03-2010, 02:45 AM   #15
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Here you go...

JAVA JRE
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Old 03-04-2010, 07:22 PM   #16
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Ok. it works now. I used tuner studio and it is very cool I changed my fuel VE at idle and the miss has not happened again since but I've only driven it a couple times since. I'm waiting for it to start again and I will datalog that thing. I'll keep my laptop on hand. thanks.
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Old 03-08-2010, 07:32 PM   #17
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I saved a few places right after the blip happens. I don't know what I'm looking for here.
Attached Thumbnails
MS missing issues.-graph1.png  
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Old 03-08-2010, 08:12 PM   #18
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That log looks like overrun might have kicked in early? dunno without the TPS.
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Old 03-08-2010, 09:40 PM   #19
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What's overrun? Yes, I'm indeed running without a TPS sensor.
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Old 03-09-2010, 11:24 AM   #20
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Overrun is a setting that's intended to turn off the injectors while coasting with your foot off the throttle to save fuel. Adjust it wrong and it will turn the injectors off during part throttle cruising.
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